Purinyl -directed aroylation of 6-arylpurine ribo- and 2'-deoxyribonucleosides, and mechanistic insights.

The purinyl ring contains four embedded nitrogen atoms of varying basicities. Selective utilization of these ring nitrogen atoms can lead to relatively facile remote functionalization, yielding modified purinyl motifs that are otherwise not easily obtained. Herein, we report previously undescribed -directed aroylation of 6-arylpurine ribo and the more labile 2'-deoxyribonucleosides.

Covalent and ionic bonding in bi- and tricyclic Group 15 amides: equidistant P-I and As-I bonds and fluxional cations.

A series of trivalent Group 15 bis(tert-butylamido)cyclodiphosph(iii)azane element bi- and tricycles of the formulae {[(tBuNP)2(tBuN)2]ElX}, El = P, As, Sb, Bi, where X = Ph, OPh, OtBu, N3, hexamethyldisilylamide (HMDS), OTf, was synthesized from the corresponding chlorides via salt elimination. The ensuing compounds were studied spectroscopically and X-ray crystallographically with a particular focus on the length of the El-X bond. While the Group 15 element to phenyl and HMDS were of normal lengths and completely covalent, those to azide appeared to be partly ionic.

The Disappearing Director: The Case of Directed -Arylation a Removable Hydroxyl Group.

A facile and broadly applicable method for the regiospecific -arylation of benzotriazoles is reported. Copper-mediated reactions of diverse 1-hydroxy-1-benzotriazoles with aryl boronic acids lead to 1-aryl-1-benzotriazole 3-oxides. A 1-OH → 3 prototropy in the 1-hydroxy-1-benzotriazoles is plausibly the underlying basis, where the tautomer is captured by the boronic acid, leading to C-N (not C-O) bond formation.

The chameleonic reactivity of dilithio bis(alkylamido)cyclodiphosph(iii)azanes with chlorophosphines.

To synthesize a bis(diphosphinylamine) ligand for use in late-metal catalysis dilithio bis(tert-butylamido)cyclodiphosph(iii)azane was treated with two equivalents of (Ph)2PCl. The chlorodiphenylphosphine attacked the dilithium salt kinetically at phosphorus, followed by a rearrangement to an unsymmetrical P, N-di-substituted product. Solid-state structures of both products were determined, and the activation energy for the rearrangement was measured.

Generating Stereodiversity: Diastereoselective Fluorination and Highly Diastereoselective Epimerization of α-Amino Acid Building Blocks.

Diastereoselective fluorination of N-Boc ( R)- and ( S)-2,2-dimethyl-4-((arylsulfonyl)methyl)oxazolidines and a previously unknown diastereoselective epimerization at the fluorine-bearing carbon atom α to the sulfone was realized. Diastereoselectivities of both reactions were excellent for benzothiazolyl sulfones, allowing access to two enantiomerically pure diastereomers from one chiral precursor. To demonstrate synthetic utility, the benzothiazolyl sulfones were converted to diastereomerically pure ( S, S)- and ( R, S)-benzyl sulfones via sulfinate salts and to amino acids.

Reactions of Germylenes and Stannylenes with Halo(hydrocarbyl)- and Chloro(amino)phosphines: Oxidative Addition versus Ligand Transfer.

Oxidative addition (OA) is an important elementary step in chemistry, but it has been studied mainly in the context of transition-metal-catalyzed reactions and mainly with carbon-X substrates (X = halogen, H). Reports of main-group metal compounds undergoing OA are rare by comparison, and those involving phosphorus-halogen substrates are rarer still. Acyclic and cyclic diazagermylenes and -stannylenes react with chloro(hydrocarbyl)phosphines with the intermediacy of oxidative addition products.

Ruthenium-Catalyzed C-H Bond Activation Approach to Azolyl Aminals and Hemiaminal Ethers, Mechanistic Evaluations, and Isomer Interconversion.

C(sp)-N bond-forming reactions between benzotriazole and 5,6-dimethylbenzotriazole with -methylpyrrolidinone, tetrahydrofuran, tetrahydropyran, diethyl ether, 1,4-dioxane, and isochroman have been conducted using RuCl•3HO/-BuOOH in 1,2-dichloroethane. In all cases, 1 and 2 alkylation products were obtained, and these are readily separated by chromatography. One of these products, 1-(isochroman-1-yl)-5,6-dimethyl-1-benzotriazole, was examined by X-ray crystallography.

Heavier carbene analogues and their derivatives as κ-El, κ2-El,N, and κ2-N,N' ligands: different reactivity patterns for acyclic and cyclic diamidogermylenes and -stannylenes.

Because of the increasing importance of N-heterocyclic carbenes in organometallic chemistry we investigated the ligand properties of structurally-related acyclic and cyclic heavier carbene analogues with transition metal chlorides. Acyclic {(Me(3)Si)(2)N}(2)El, El = Ge and Sn, react with CuCl with transfer of one (Me(3)Si)(2)N ligand to yield the known copper tetramer {(Me(3)Si)(2)NCu}(4). The cyclic Me(2)Si(μ-N(t)Bu)(2)Ge, by contrast, binds copper through germanium only, furnishing a tetranuclear ladder structure with both terminal and bridging germylenes.

Syntheses and structures of cationic and neutral, homo- and heteroleptic tert-butoxides of the group 4 metals.

The utility of tri-tert-butoxystannate as a chelating tridentate ligand for group 4 metals was investigated. The highly Lewis acidic metals degraded the stannate ion in a series of tert-butoxide abstraction steps to produce a variety of group 4 tert-butoxides. A total of 1 equiv of NaSn(O(t)Bu)(3) reacted with cis-MCl(4)(THF)(2) [M = Zr (1), Hf (2)] in THF solutions to furnish the salts fac-{[M(O(t)Bu)(3)(THF)(3)](SnCl(3))}, which are separated ion pairs featuring weakly coordinating trichlorostannate ions.

Reversal of polarization in amidophosphines: neutral- and anionic-kappaP coordination vs. anionic-kappaP,N coordination and the formation of nickelaazaphosphiranes.

Nickel(ii) chloride reacts with the bis(tert-butylamino)diazadiphosphetidine {Bu(t)(H)NP(micro-NBu(t))(2)PN(H)Bu(t)} to form trans-[{Bu(t)(H)NP(micro-NBu(t))(2)PN(H)Bu(t)}(2)NiCl(2)]. In solution and the solid-state each heterocyclic ligand coordinates nickel through one phosphorus atom only. For comparison the solid-state structure of the known trans-[NiCl(2)(PEt(3))(2)] was also determined and it was found that the two complexes have almost identical bond parameters about nickel.

Inorganic heterocyclic bis(phosphines): syntheses and structures of a 1,2-bis(diazasilaphosphetidino)ethane and its nickel, molybdenum, and rhodium complexes.

Synthesis and characterization of a new, highly electron-rich, chelating bis(phosphine), based on the ethanediyl-linked inorganic heterocycle [Me(2)Si(mu-N(t)Bu)(2)P], are reported. Treatment of nickel chloride with this bis(phosphine) afforded square-planar cis-[[Me(2)Si(mu-N(t)Bu)(2)PCH(2)](2)NiCl(2)], which features isometric nickel-chloride (2.2220(8) A) and nickel-phosphorus (2.

Syntheses and structures of P-anilino-P-chalcogeno- and P-anilino-P-iminodiazasilaphosphetidines and their group 12 and 13 metal compounds.

The P-anilino-P-chalcogeno(imino)diazasilaphosphetidines [Me(2)Si(mu-N(t)Bu)(2)P=E(NHPh)] (E = O (3), S (4), Se (5), N-p-tolyl (6)) were synthesized by oxidizing the P-anilinodiazasilaphosphetidine [Me(2)Si(N(t)Bu)(2)P(NHPh)] (2) with cumene hydroperoxide, sulfur, selenium, and p-tolyl azide, respectively. The lithium salt of 4 reacted with thallium monochloride to produce ([Me(2)Si(mu-N(t)Bu)(2)P=S(NPh)-kappaN-kappaS]Tl)(7), which features a two-coordinate thallium atom. Treatment of 4-6 with AlMe(3) gave the monoligand dimethylaluminum complexes ([Me(2)Si(mu-N(t)Bu)(2)P=E(NPh)-kappaN-kappaE]AlMe(2)) (E = S (8), Se (9), N-p-tolyl (10)), respectively.

Monomeric, Four-Coordinate Group 4 Metal Complexes with Chelating Bis(tert-butylamido)cyclodisilazane Ligands: Syntheses and Molecular Structures of {(MeSiN(t)Bu)(2)(N(t)Bu)(2)}MCl(2) and {(MeSiN(t)Bu)(2)(N(t)Bu)(2)}MMe(2), M = Zr, Hf.

The interaction of (MeSiN(t)Bu)(2)(N(t)BuLi)(2) with MCl(4) in hot toluene produces {(MeSiN(t)Bu)(2)(N(t)Bu)(2)}MCl(2,) M = Zr (1), Hf (2), in good yields. The light-yellow and colorless solids are isostructural and crystallize in the monoclinic crystal system, space group P2(1)/n, with four molecules in the unit cell. The unit cell dimensions for 1 (293 K) are a = 9.

Formation of Metal Clusters or Nitrogen-Bridged Adducts by Reaction of a Bis(amino)stannylene with Halides of Two-Valent Transition Metals.

When the cyclic bis(amino)stannylene Me(2)Si(NtBu)(2)Sn is allowed to react with metal halides MX(2) (M = Cr, Fe, Co, Zn; X = Cl, Br [Zn]) adducts of the general formula [Me(2)Si(NtBu)(2)Sn.MX(2)](n) are obtained. The compounds are generally dimeric (n = 2) except the ZnBr(2) adduct, which is monomeric in benzene.